Phylogenetic analysis of the 5′ subterminal region of isolates ofLeishmaniaRNA virus-1

Abstract

Leishmania RNA virus-1 (LRV1) is a double-stranded RNA virus present in some Leishmania species. The virus genome consists of a 450-nucleotide, 5′ untranslated region (UTR) followed by the coat gene and the RNA-dependent RNA polymerase (RDRP). It has been shown that the 5′ end UTR of the genome promotes internal initiation of translation in an in-vitro assay, indicating the presence of an internal ribosomal entry site (IRES) element upstream of the coat gene. The nucleotide sequences of the 5′ subterminal regions of six new isolates of LRV1, of different geographical origins, have now been determined. The RNA folding of the 5′ subterminal region of LRV1 has been predicted, using a combination of thermodynamic parameters and folding constraints based on nucleotide substitutions. Furthermore, a putative pyrimidine-rich region (a feature unique to all IRES elements), which is complementary to the Leishmania 18S rRNA, has been identified. The significance and relevance of these findings in the context of the function of the 5′ UTR of LRV1 as an IRES element are discussed.